8.1, compression, 32bit, 64bit and snapmirror medley

I'm trying to SM a 64bit volume to a new volume in a 32bit aggregate. Both filers are running 8.1.3 so I believe this should work. I enabled compression on the 64 bit volume and SM complained that the destination aggregate doesn't support it so it'll no longer work. I've since disabled compression but it still complains presumably because some blocks are compressed.

So, as I can't change the aggregate to 64bit because there's no way to do it without adding disks which I don't have, is there a way to uncompressed the data that's been compressed?